1. Field of the Invention
The present invention relates to a current supply circuit and a control method for a supply current to a reel-drive motor in a magnetic apparatus.
2. Description of the Related Art
There is known a magnetic tape apparatus of a type that a magnetic tape is transferred from a supply reel to a take-up reel through a magnetic head, such that tape tension in the vicinity of the magnetic head is maintained at a constant value without a mechanical tape buffer which applies mechanical tension to the magnetic tape.
In such a magnetic tape apparatus, in order to transfer the magnetic tape from the supply reel to the take-up reel at a constant tape tension and a constant tape speed, the reel-drive motor must be controlled under a torque corrected by various parameters, for example, a reference torque, a difference torque caused by a change in the radius of a magnetic tape wound on the reel (below, a radius of a tape), a friction torque caused by the reel, and an inertial moment caused by the rotation of the reel.
A current supply circuit is provided for supplying the current to the reel-drive motor in accordance with a command that is generated in response to the radius of the tape and the actual tape speed so that it is possible to apply the corrected torque to the reel-drive motor.